Terpolymer systems for electromechanical and dielectric applications

ABSTRACT

There are disclosed new polymer materials having improved electric field induced strain levels, dielectric constants, and elastic energy densities for use in electromechanical and dielectric applications. Methods of manufacture of new polymer materials are also disclosed.

[0001] This application claims priority from U.S. ProvisionalApplication No. 60/280,303, filed Mar. 30, 2001, and is acontinuation-in-part application of U.S. Ser. No. 09/195,061, filed Nov.18, 1998.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to polymeric materials withelevated electric field induced strain levels, elevated elastic energydensities, and having elevated dielectric constants at room temperature.The material can be used in electromechanical devices which convertelectric energy into mechanical energy or convert mechanical energy intoelectric energy. Material of the invention can also be used as acapacitor which stores electric energy and regulates electric voltage ina circuit.

[0004] 2. Description of the Prior Art

[0005] Both polymers and inorganic materials (such as ceramics) havebeen used widely in electromechanical devices such as actuators,transducers, artificial muscles and robots. However, in the currentlyavailable commercial materials, the strain level and elastic energydensity both are quite low (strain ˜0.1% and elastic density ˜0.1J/cm³), which causes many problems for device performance. For example,in order to generate large actuation, in many current devices, anamplification scheme has to be used. In addition, the low elastic energydensity also reduces the force and power output of the electromechanicaldevices. In order to improve the performance of a wide variety ofelectromechanical devices, it is required that the electric fieldinduced strain level and elastic energy density be improved.

[0006] Polymers are also used widely in capacitors for high voltageoperation and charge storage. However, the dielectric constant of thecurrent commercial polymers is quite low (below 10). A high dielectricconstant polymer can reduce the capacity volume and charge storagecapability of the capacity.

[0007] In spite of their advantages over the ceramics, current polymerssuffer low field sensitivities, such as dielectric constant,piezoelectric coefficient, electromechanical coupling factor and fieldinduced strain. These constraints severely limit the application offerroelectric polymers as transducers, sensors and actuators.

[0008] There is a demand for improved materials for use in actuators andtransducers due to the limitations of currently available materials. Forexample, current actuator materials, such as electrostatic,electromagnetic and piezoelectric materials, exhibit limitations in oneor more of the following performance parameters: strain, elastic energydensity, speed of response and efficiency. For instance, piezoceramicand magnetostrictive materials, while possessing low hysteresis and highresponse speeds, suffer from low strain levels (˜0.1%). Shape memoryalloys generate high strain and high force but are often associated withlarge hysteresis and very slow response speeds. On the other hand, thereare several polymers such as polyurethane, polybutadine etc. which cangenerate high electric field induced strain i.e. up to 6-11%. But, dueto their low elastic modulus, their elastic energy density is very low.Further, the strain generated in these materials is mainly due to theelectrostatic effect, which is a low frequency process. Use of thesematerials at high frequencies reduces their response drastically. Inaddition, due to their low dielectric constant, the electric energydensity of these polymers is very low which is an undesirablecharacteristic for many transducer and actuator applications.

[0009] Substantial efforts have been devoted to improvement of phaseswitching materials where an antiferroelectric and ferroelectric phasechange can be field induced to cause a high strain in the material.While strains higher than 0.7% have been achieved in such materials, dueto the brittleness of ceramics, severe fatigue has been found to occurat high strain levels. Recently, in a single crystal ferroelectricrelaxor, i.e., PZNPT, an electric field strain of about 1.7%, with verylittle hysteresis, has been reported, which is exceptionally high for aninorganic materials (see: Park and Shrout, J Appl. Phys., 82, 1804(1997)). In such ceramic materials, mechanical fatigue occurs at highstrain levels, a major obstacle limiting their use for manyapplications.

[0010] For many applications, such as microrobots, artificial muscles,vibration controllers, etc., higher strain levels and higher energydensities are required. Thus, there is a need for a general purposeelectroactive material with improved performance for use with transducerand actuators.

[0011] There is a further requirement for improved ultrasonictransducers and sensors for use in medical imaging applications and lowfrequency acoustic transducers. Current piezoceramic transducermaterials, such as PZTs, have a large acoustic impedance (Z>35 Mrayls)mismatch with the air and human tissue (Z<2 Mrayls). On the other hand,piezoelectric polymers such as P(VDF-TrFE), PVDF not only have anacoustic impedance well matched (Z<4 Mrayls) to human tissue but alsooffer a broad nonresonant frequency bandwidth. But, because of their lowpiezoelectric activity and low coupling coefficient, the sensitivity ofsuch ultrasonic polymer transducers is very low.

[0012] The capacitor industry also requires a capacitor which has a muchhigher electric energy density than is currently available. Currentdielectric materials, such as polymers, have a low dielectric constant(˜2-10) and limited energy density. In addition, with current ceramics,the maximum field which can be applied is limited.

[0013] Accordingly, it is an object of the invention to provide apolymeric material which can generate a high electric field-inducedstrain with little hysteresis.

[0014] It is another object of the invention to provide a polymericmaterial which exhibits a high elastic energy density.

[0015] It is yet another object of the invention to provide a polymericmaterial that exhibits a room temperature dielectric constant that ishigher than other currently available polymers.

[0016] These and other objects and advantages of the present inventionand equivalents thereof, are achieved by compositions for electrical orelectomechanical devices.

SUMMARY OF THE INVENTION

[0017] The present invention provides polymers prepared by apolymerizing a mixture of three monomers comprising: at least onemonomer of vinylidene-fluoride; at least one monomer selected from thegroup consisting of trifluorethylene and tetrafluoroethylene; and atleast one monomer selected from the group consisting oftetrafluorethylene, vinyl fluoride, perfluoro (methyl vinyl ether);bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene,and hexafluoroethylene. Polymers of the invention exhibit anelectrostrictive strain, at room temperature, of 3% or more when anelectric field gradient of 100 megavolts per meter or greater is appliedthereacross, exhibit a dielectric constant, at room temperature, of 40or higher at 1 kHz, and exhibit an elastic energy density, at roomtemperature, of 0.3 joules/cm³ or higher, or any combinations thereof.

[0018] The present invention also provides a process for the preparationof polymers comprising: polymerizing a mixture of three monomerscomprising at least one monomer of vinylidene-fluoride; at least onemonomer selected from the group consisting of trifluorethylene andtetrafluoroethylene; and at least one monomer selected from the groupconsisting of tetrafluorethylene, vinyl fluoride, perfluoro (methylvinyl ether), bromotrifluoroethylene, chlorofluoroethylene,chlorotrifluoroethylene, and hexafluoroethylene; stretching said polymergreater than its original length; and thereafter annealing said polymerat a temperature below its melting point, wherein said polymer exhibitsan electrostrictive strain, at room temperature, of 3% or more when anelectric field gradient of 100 megavolts per meter or greater is appliedthereacross, exhibits a dielectric constant, at room temperature, of 40or higher at 1 kHz, and exhibits an elastic energy density, at roomtemperature, of 0.3 joules/cm³ or higher, or any combinations thereof.

[0019] Also provided are electrical or electromechanical devicescomprising at least one layer of a polymer of the invention. Polymersinclude, but are not necessarily limited to, polyvinylidenefluoride-trifluorethylene-chlorofluoroethylene P(VDF-TrFE-CFE),polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethyleneP(VDF-TrFE-CTFE), polyvinylidenefluoride-tetrafluoroethylene-chlorotrifluoroethylene, polyvinylidenefluoride-trifluorethylene-hexafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-hexafluoroethylene, polyvinylidenefluoridetrifluorethylene-tetrafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-tetrafluoroethylene, polyvinylidenefluoridetrifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a graph of electric field induced logitudinal strain asa function of the applied field amplitude for the terpolymerP(VDF-TrFE-CTFE). The terpolymer No. 49 is 72.2/17.8/1 0 mol %; theterpolymer No. 52 is 66/22.5/11.5 mol %; and the third embodiment of thegraph is the terpolymer 58.5/31.5/10 mol %. All measurements were madeat room temperature.

[0021]FIG. 2 is a graph of the field induced transverse strain as afunction of the applied field amplitude for the uniaxially stretchedterpolymer P(VDF-TrFE-CTFE), 63.1/25.4/11.5 mol % measured at roomtemperature.

[0022]FIG. 3 is a graph of the strain hysteresis loop for the terpolymerP(VDF-TrFE-CTFE), 58.5/31.5/10 mol %.

[0023]FIG. 4a and FIG. 4b are graphs of the dialectric constant andloss, respectively, as a function of temperature of the terpolymerP(VDF-TrFE-CTFE) in the frequency range from 100 Hz to 1 MHz (dielectricconstant: from the top to bottom: 100, 300, 1k, 3k, 10k, 30k, 100k,300k, and 1 MHz) (dielectric loss: from the bottom to top: 100, 300, 1k,3k, 10k, 30k, 100k, 300k, and 1 MHz).

[0024]FIG. 5. Is a graph of the field induced longitudinal strain as afunction of the applied field amplitude for the terpolymerP(VDF-TrFE-CFE), 60/36/4 mol % measured at room temperature.

DETAILED DESCRIPTION OF THE INVENTION

[0025] It was found that in certain classes of terpolymer systems suchas P(VDF-TrFE-CTFE) (poly(vinylidenefluoride-trifluorethylene-chlorotrifluoroethylene)) and P(VDF-TrFE-CFE)(poly(vinylidene fluoride-trifluorethylene-chlorofluoroethylene)), anultrahigh electric field induced strain can be achieved. InP(VDF-TrFE-CTFE), as shown in FIG. 1, a thickness strain of −4% can beinduced. If the terpolymer is mechanically stretched (4 to 5 times ofthe original length) and annealed afterwards at a temperature 5 to 15degrees below the melting temperature of the polymer, a large fieldinduced transverse strain ( 3%), see FIG. 2, can be obtained.Electrostrictive strains of about 3% or above are preferred. Inaddition, the terpolymer has an elastic modulus at room temperature of0.5 GPa, which results in an elastic energy density (per unit volume)˜0.4 J/cm³. Preferred elastic energy densities of terpolymers of theinvention are ˜0.3 J/cm³ or above. Such a large strain with a very lowhysteresis (see FIG. 3) is very useful for electromechanical devices.

[0026] It was also found that the P(VDF-TrFE-CTFE) terpolymer has a veryhigh room temperature dielectric constant (c.f., FIG. 4), at 100 Hz, theroom temperature dielectric constant can be more that 65, which issignificantly higher than any commercial polymers. Dielectric constantsof the terpolymers of the invention are preferably 40 or above.

[0027] For those applications, the composition of the terpolymerP(VDF_(x)-TrFE_(y)-CTFE_(1-x-y)) should be: x is in the range of0.55-0.75 and y in the range of 0.15-0.35.

[0028] In P(VDF-TrFE-CFE) terpolymer system, as shown in FIG. 5, thereis also a large thickness strain induced electrically. In thisterpolymer (60/36/4 mol %, P(VDF_(x)-TrFE_(y)-CFE_(1-x-y))), arelatively high thickness strain (−4.5%) can be induced under a field˜150 MV/m The terpolymer also exhibits a high elastic modulus ˜1 GPawhich results in an elastic energy density ˜1 J/cm³, much higher thanthose in the piezoelectric materials. For this terpolymer system, thecomposition range of P(VDF_(x)-TrFE_(y)-CFE_(1-x-y)) x should be in therange of 0.55-0.8 and y in the range of 0.15-0.4.

[0029] The high strain and high elastic energy density discovered in theterpolymer systems here are very attractive because it is well knownthat polymers can withstand high elastic strains without fatigue. Thisis a clear advantage over any inorganic material where the fatigue athigh mechanical strain is a serious problem for the electromechanicaldevice applications.

[0030] The present invention discloses a series of terpolymer systemswhich preferably exhibit high electric field induced strain with highelastic energy density and also high room temperature dielectricconstant. The terpolymer systems include poly(vinylidenefluoride-trifluorethylene-chlorofluoroethylene), poly(vinylidenefluoride-trifluorethylene-vinylidene chloride), poly(vinylidenefluoride-trifluorethylene-tetrafluoroethylene), poly(vinylidenefluoride-trifluorethylene-vinyl fluoride), poly(vinylidenefluoride-trifluorethylene-perfluoro(Methyl vinyl ether)),poly(vinylidene fluoride-trifluorethylene-bromotrifluoroethylene),poly(vinylidene fluoride-trifluorethylene-chlorofluoroethylene), andpoly(vinylidene fluoride-trifluorethylene-vinylidene chloride).

[0031] High strain and high dielectric constant polymer systems, highenergy irradiated P(VDF-TrFE) copolymers, have been earlier disclosed.An advantage of the current terpolymer systems is that the irradiationstep used with the copolymer systems is eliminated. This savesmanufacture cost and improves the reliability and reproducibility of theelectroactive polymer systems.

[0032] Polymers of the present invention are conveniently prepared orsynthesized by polymerizing processing known in the art, such assuspension, emulsion, or solutions methods. Three monomers (i.e., VDF.TrFE, CFE) are selected and contacted or mixed in proportion in thepresence of a suitable catalyst or initiator. The resultant terpolymersystems should have a convenient molecular weight suitable for use inelectrical or electromechanical devices. The molecular weight of thepolymer systems of the present invention is not limited. The molecularweight of terpolymers is preferably, but not limited to, higher thanabout 50,000, more preferably higher than 100,000, and yet morepreferably from about 100,000 to about 300,000.

[0033] Although the present invention describes in detail certainembodiments, it is understood that variations and modifications existknown to those skilled in the art that are within the invention.Accordingly, the present invention is intended to encompass all suchalternatives, modifications and variations that are within the scope ofthe invention as set forth in the following claims.

What is claimed is:
 1. A polymer prepared by a polymerizing a mixture ofthree monomers comprising: at least one monomer of vinylidene-fluoride;at least one monomer selected from the group consisting oftrifluorethylene and tetrafluoroethylene; and at least one monomerselected from the group consisting of tetrafluorethylene; vinylfluoride; perfluoro (methyl vinyl ether); bromotrifluoroethylene;chlorofluoroethylene; chlorotrifluoroethylene; and hexafluoroethylene.2. The polymer of claim 1, wherein said polymer is selected from thegroup consisting of polyvinylidenefluoride-trifluorethylene-chlorofluoroethylene P(VDF-TrFE-CFE),polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethyleneP(VDF-TrFE-CTFE), polyvinylidenefluoride-tetrafluoroethylene-chlorotrifluoroethylene, polyvinylidenefluoride-trifluorethylene-hexafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-hexafluoroethylene, polyvinylidenefluoride-trifluorethylene-tetrafluoroethylene, polyvinylidenefluoridetetrafluorethylene-tetrafluoroethylene, polyvinylidenefluoridetrifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylene-vinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 3. Thepolymer of claim 1, wherein said polymer is polyvinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene having a ratio ofmonomers represented as P(VDF_(x)-TrFE_(y)-CTFE_(1-x-y)), wherein x isabout 0.55 to about 0.75, y is about 0.15 to about 0.35.
 4. The polymerof claim 1, wherein said polymer is polyvinylidenefluoride-trifluorethylene-hexafluoroethylene having a ratio of monomersrepresented as P(VDF_(x)-TrFE_(y)-HFP_(1-x-y)), wherein x is about 0.55to about 0.75, and y is about 0.15 to about 0.4.
 5. A polymer of claim1, wherein said polymer exhibits an electrostrictive strain, at roomtemperature, of 3% or more when an electric field gradient of 100megavolts per meter or greater is applied thereacross.
 6. The polymer ofclaim 5, wherein said polymer is selected from the group consisting ofpolyvinylidene fluoride-trifluorethylene-chlorofluoroethyleneP(VDF-TrFE-CFE), polyvinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene P(VDF-TrFE-CTFE),polyvinylidene fluoride-tetrafluoroethylene-chlorotrifluoroethylene,polyvinylidene fluoride-trifluorethylene-hexafluoroethylene,polyvinylidene fluoride-tetrafluorethylene-hexafluoroethylene,polyvinylidene fluoride-trifluorethylene-tetrafluoroethylene,polyvinylidene fluoride-tetrafluorethylene-tetrafluoroethylene,polyvinylidene fluoride-trifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 7. Apolymer of claim 1, wherein said polymer exhibits a dielectric constant,at room temperature, of 40 or higher at 1 kHz.
 8. The polymer of claim7, wherein said polymer is selected from the group consisting ofpolyvinylidene fluoride-trifluorethylene-chlorofluoroethyleneP(VDF-TrFE-CFE), polyvinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene P(VDF-TrFE-CTFE),polyvinylidene fluoride-tetrafluoroethylene-chlorotrifluoroethylene,polyvinylidene fluoride-trifluorethylene-hexafluoroethylene ,polyvinylidene fluoride-tetrafluorethylene-hexafluoroethylene, polyvinylidene fluoride-trifluorethylene-tetrafluoroethylene, polyvinylidenefluoridetetrafluorethylene-tetrafluoroethylene, polyvinylidenefluoride-trifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether), polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 9. Apolymer of claim 1, wherein said polymer exhibits an elastic energydensity, at room temperature, of 0.3 joules/cm³ or higher.
 10. Thepolymer of claim 8, wherein said polymer is selected from the groupconsisting of polyvinylidenefluoride-trifluorethylene-chlorofluoroethylene P(VDF-TrFE-CFE),polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethyleneP(VDF-TrFE-CTFE), polyvinylidenefluoride-tetrafluoroethylene-chlorotrifluoroethylene, polyvinylidenefluoride-trifluorethylene-hexafluoroethylene , polyvinylidenefluoride-tetrafluorethylene-hexafluoroethylene, polyvinylidenefluoride-trifluorethylene-tetrafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-tetrafluoroethylene, polyvinylidenefluoride-trifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 11. Anelectrical or electromechanical device comprising at least one layer ofa polymer of claim
 1. 12. The electrical or electromechanical device ofclaim 11, wherein Said polymer is selected from the group consisting ofpolyvinylidene fluoride-trifluorethylene-chlorofluoroethyleneP(VDF-TrFE-CFE), polyvinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene P(VDF-TrFE-CTFE),polyvinylidene fluoride-tetrafluoroethylene-chlorotrifluoroethylene,polyvinylidene fluoride-trifluorethylene-hexafluoroethylene ,polyvinylidene fluoride-tetrafluorethylene-hexafluoroethylene,polyvinylidene fluoride-trifluorethylenete-trafluoroethylene,polyvinylidene fluoride-tetrafluorethylene-tetrafluoroethylene,polyvinylidene fluoride-trifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylene-vinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride5 tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylenepolyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 13. Aprocess for the preparation of a polymer comprising: polymerizing amixture of three monomers comprising at least one monomer ofvinylidene-fluoride; at least one monomer selected from the groupconsisting of trifluorethylene and tetrafluoroethylene; and at least onemonomer selected from the group consisting of tetrafluorethylene; vinylfluoride; perfluoro (methyl vinyl ether); bromotrifluoroethylene;chlorofluoroethylene; chlorotrifluoroethylene; and hexafluoroethylene;stretching said polymer greater than its original length; and thereafterannealing said polymer at a temperature below its melting point, whereinsaid polymer exhibits an electrostrictive strain, at room temperature,of 3% or more when an electric field gradient of 100 megavolts per meteror greater is applied thereacross, exhibits a dielectric constant, atroom temperature, of 40 or higher at 1 kHz, and exhibits an elasticenergy density, at room temperature, of 0.3 joules/cm³ or higher, or anycombinations thereof.
 14. The process of claim 13, wherein said polymeris stretched at least four times its original length.
 15. The process ofclaim 13, wherein said polymer is annealed at a temperature of at least1° F. below its melting point, preferably from 1° F. to 30° F. below itsmelting point, and more preferably from 5° F. to 15° F. below itsmelting point.
 16. The process of claim 13, wherein said polymer isselected from the group consisting of polyvinylidenefluoride-trifluorethylene-chlorofluoroethylene P(VDF-TrFE-CFE),polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethyleneP(VDF-TrFE-CTFE), polyvinylidenefluoride-tetrafluoroethylene-chlorotrifluoroethylene, polyvinylidenefluoride-trifluorethylene-hexafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-hexafluoroethylene, polyvinylidenefluoride-trifluorethylene-tetrafluoroethylene, polyvinylidenefluoride-tetrafluorethylene-tetrafluoroethylene, polyvinylidenefluoridetrifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinyl idene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.
 17. Apolymer prepared by prepared by a polymerizing a mixture of threemonomers comprising: at least one monomer of vinylidene-fluoride; atleast one monomer selected from the group consisting of oftrifluorethylene and tetrafluoroethylene; and at least one monomerselected from the group consisting of tetrafluorethylene; vinylfluoride; perfluoro (methyl vinyl ether); bromotrifluoroethylene;chlorofluoroethylene; chlorotrifluoroethylene; and hexafluoroethylene,wherein said polymer exhibits an electrostrictive strain, at roomtemperature, of 3% or more when an electric field gradient of 100megavolts per meter or greater is applied thereacross, exhibits adielectric constant, at room temperature, of 40 or higher at 1 kHz, andexhibits an elastic energy density, at room temperature, of 0.3joules/cm³ or higher, or any combinations thereof.
 18. The polymer ofclaim 17, wherein said polymer is selected from the group consisting ofpolyvinylidene fluoride-trifluorethylene-chlorofluoroethyleneP(VDF-TrFE-CFE), polyvinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene P(VDF-TrFE-CTFE),polyvinylidene fluoride-tetrafluoroethylene-chlorotrifluoroethylene,polyvinylidene fluoride-trifluorethylene-hexafluoroethylene,polyvinylidene fluoride-tetrafluorethylene-hexafluoroethylene,polyvinylidene fluoride-trifluorethylene-tetrafluoroethylene,polyvinylidene fluoride-tetrafluorethylene-tetrafluoroethylene,polyvinylidene fluoridetrifluorethylene-vinyl fluoride, polyvinylidenefluoride-tetrafluorethylenevinyl fluoride, polyvinylidenefluoride-trifluorethylene-perfluoro(methyl vinyl ether), polyvinylidenefluoride-tetrafluorethylene-perfluoro(methyl vinyl ether),polyvinylidene fluoride-trifluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-bromotrifluoroethylene,polyvinylidene fluoride-tetrafluorethylene-chlorofluoroethylene,polyvinylidene fluoride-trifluorethylene-vinylidene chloride, andpolyvinylidene fluoride-tetrafluorethylene-vinylidene chloride.